Experimental analysis of the addition and substitution of sub-bituminous pulverized coal in a natural gas premixed flame

•Pulverized coal addition to natural gas increases the radiation intensity.•The natural gas flame front was lengthened by the addition of pulverized coal.•Turbulence intensity had no significant effect on the radiation intensity. This paper presents the experimental results of the addition (increasing thermal power) and substitution (constant thermal power) of a sub-bituminous pulverized coal in a natural gas flame in a laboratory-scale premixed burner. The analyzed variables include radiation intensity, temperature profile, and flame shape. It was found that with the addition of 15% and 30% coal (energy based) into the natural gas flame, the radiation intensity was increased by 37% and 65%, respectively. However, with the substitution of 15% and 30% coal for methane (energy based), the radiation intensity was reduced by 10% and 61%, respectively. Additionally, regarding the flame temperature, it was observed that 30% coal addition increased temperature by approximately 5%, while 30% coal substitution led to a reduction in flame temperature of 35%. Regarding flame shape, it was found that increased turbulence shortened the flame, while both the addition and substitution of coal into a methane flame lengthened the reaction zone.